Ocneria terebinthina Strg. (Lep.: Lymanteriidae) is a leaf borer pest in pistachio orchard. The toxicity of Bacillus thuringiensis var. kurstaki alone and in combination with henna powder was investigated on third larval instar of O. terebinthina under laboratory conditions. Bioassay was carried out using spray technique on pistachio offshoot. Probit analysis of concentration-mortality data was conducted to estimate the LC50 value. The LC50 value of B. thuringiensis on third instar of larvae was estimated as 2817.30 ppm. The synergist effect of henna powder on efficacy of B. thuringiensis was also evaluated. Three concentrations of henna powder were combined with minimum lethal dose of B. thuringiensis against third larval instar. The results revealed that the henna powder had synergist effect on B. thuringiensis. The combination of B. thuringiensis and henna powder (6000 ppm) caused 80.68% mortality, whereas B. thuringiensis alone caused 15.91% mortality. Our results suggested that henna powder can increase the efficacy of B. thuringiensis in controlling O. terebinthina in pest integrated management.